1. Field of Invention
The present invention relates to a container closure and more particularly to an improved tear-off closure having an integral, concentric pull ring for manually removing the closure from a container on which it is sealed.
2. Description of the Prior Art
The well-known crown seal closure for beverage bottles has been in use since the late nineteenth century. Since the only practical method of removing the crown seal bottle cap is with an auxiliary tool such as the conventional bottle opener, there have been many efforts to design a bottle cap which does not require such tools. One result of such efforts was the development of twist-off or screw-off closures. In order to employ these screw-off closures, the exterior surface of the bottle mouth must have a threaded finish for securing the screw-off closure on the bottle.
Some ecology oriented groups are demanding the use of returnable beverage bottles as an ecological attempt to reduce the quantity of unsightly litter. A few jurisdictions have also enacted legislation which encourages use of returnable bottles. Approximately two-thirds of the existing returnable beverage bottles have crowned rather than threaded finishes. With approximately forty billion crown seal bottles in circulation today, an easily removable replacement for the crown seal bottle cap is desirable.
A tear-off closure having an integral, concentric pull ring for removing the closure from the container is discloseed in Coop U.S. Pat. No. 3,865,268. The cap wall of that closure terminates in a bead and has a sever line between the bead and cap wall to enable severing of a major portion of the bead from the closure during capping. The severed bead forms a pull ring for pulling the closure from the container. The unsevered portion of the bead integrally connects the pull ring to the cap wall. In such cap, the sever line intersects with a pair of score lines formed on the closure defining a tear strip which is easily severed from the cap when the ring is pulled upwardly.
The score lines that define the tear strip in the body of the closure of U.S. Pat. No. 3,865,268 are preferably formed in the flat blank before the blank is drawn into a cup shape. The sever line which defines the pull ring is formed after drawing the blank into the cup shape. Utilizing such two step process makes it difficult to perfectly align the sever line with the score lines such that the terminal ends coincide. If the sever line is out of alignment such that it terminates inwardly of the score lines inside the tear strip, the pull ring may be torn from the tear strip when attempting to remove the closure.
Intersection of the sever line with both score lines in the thin cap wall of the closure of U.S. Pat. No. 3,865,268 may also cause the closure to be weak at such points of intersection. The impace of such weakness is apparent when considering that beer and other beverages, especially carbonated beverages, may exert a force in excess of ninety pounds per square inch against the under surface of the applied bottle cap. Such pressure may effect premature rupturing of the tear strip of the closure at the points where the sever line intersects the score lines of the tear strip.
Accordingly, an improved tear-off closure is desired which will assure that after the capping operation, the closure is able to withstand high internal pressures while maintaining the advantage of being relatively easy to open manually without need for a bottle opener.